The bearing arrangement of the telescopic parts of telescopic crane jibs, and in particular the slide bearing between telescopic parts, influences the load bearing characteristics of the jib as a whole to a high degree. This factor has assumed even greater importance in recent times due to the fact that high tensile materials permit a more lightweight construction of the telescopic parts. Because of the resulting thinner wall thicknesses, bigger deformations can occur in the region of the sliding bearing and in the jib as a whole. In order to keep deformations to an absolute minimum and thus optimise the load bearing characteristics, negative influences from other sources must be minimised. For example, the mounting or the slide mounting of the telescopic parts must be designed so that the load carrying capacity is impaired as little as possible. To this end, it is important to support the slide bearing arrangement in its cross-sectional regions that are most exposed to risk in terms of stability and prevent uneven carrying behaviour and hence additional moments occurring in cross-sectional regions subjected to high loads.
Conventional slide bearings have slide blocks, which are mounted between the telescopic parts. Such slide blocks are of a specific width, which renders adjustments and readjustments difficult because it is necessary to replace the slide block with a wider or narrower one, for example. Abrasion during operation can also give rise to bearing defects and the subsequent adjustment or replacement work is time-consuming and expensive.
The present invention is directed to a slide bearing arrangement for telescopic crane jibs which overcomes the problems outlined above. In particular, the slide bearing arrangement of the invention is adaptable to a specific telescopic crane jib and permits a uniform load bearing characteristics over a long service life without major expense.
The invention comprises a telescopic crane jib slide bearing part which has a receiving means and a filler compound which is introduced into the receiving means. Based on a construction of this type, the slide bearing part can be adapted to any situation in the bearing gap without the need for further measures and can be adapted simply by introducing a specific filler compound in a specific way, or by introducing a specific quantity of filler compound into the receiving means until the optimum shape is achieved for the slide block. As a result an optimum shape adaptation and conformity can be achieved with respect to the abutting telescopic parts, using a bearing of a simple design and simple manufacture. The telescopic parts can be mutually aligned without any major effort and can also be changed if necessary.
The receiving means of the invention may be a hollow body, in particular a hollow section or a hose-shaped hollow body.
Alternatively, the receiving means may also be provided in the form of a shell. Such a shell forms a peripheral boundary and the cavity between two telescopic parts can be filled out with friction-resistant and abrasion resistant plastic material using an injection casting process. The adaptability and conformity advantages of the invention are also realized with this system.
The receiving means is preferably made from a material that is capable of conforming to a shape and may contain a friction-resistant and abrasion-resistant material, in particular a polyamide or polyethylene reinforced with glass fibre.
According to the invention, the filler compound may contain a material which can be solidified, such as by curing, and which is capable of conforming to a shape. It may be pressed, injected or injection-cast into the receiving means. In particular, the filler compound may be made from one or more of the following materials or contain one or more of the following materials:                a thermoplastic material;        a thermosetting plastic, in particular in the form of a casting resin or a moulding compound with or without fibre reinforcement;        a plastic foam;        a liquid that is capable of crystallisation, in particular sodium acetate; and/or        an elastomer.        
A Teflon core (PTFE) may be accommodated in the receiving means. In particular, a Teflon core may be incorporated in the hollow sections or hoses, and a compression force may be applied from outside, for example, as a result of which, because of its viscous properties, it fills out the gap between the telescoping sections. Once the receiving means has been closed, therefore, a uniform and balancing force distribution can be achieved during operation, depending on the load state.
The present invention further comprises a telescopic crane jib slide bearing part which has one or more slide bearing parts, as described above. If several slide bearing parts are provided, they may be disposed in a mutually abutting arrangement. It is also possible for the outer frames of the slide bearing parts in a slide bearing to be of the same or different lengths as a means of adapting to a specific application.
One advantageous feature of a slide bearing according to the invention is that filaments may be provided in the receiving means, between the slide bearing parts or at their edges. These filaments may be used for plasticizing or liquefying the material by means of heat in order to achieve conformation to the appropriate shapes.
The present invention relates to a telescopic bearing arrangement for a telescopic crane jib comprising at least one slide bearing part, as described above. The slide bearing may be disposed between two adjacent telescopic parts or sections of the jib, for example in the collar of an outer telescopic part and/or in the base piece of an inner telescopic part. The slide bearing parts may be disposed partially or fully over the entire overlap areas and are used to support areas of the jib that are more at risk in terms of stability when subjected to high thrust loads.
The telescopic slide bearing arrangement according to the invention may include abutments provided in the end frames and/or on the jib sections, which are engaged by the receiving means filled with the filler compound. Such an arrangement secures the bearings axially and/or in the circumferential direction. The abutment may be provided in the form of a locating or engaging arrangement, in particular as a bead arrangement, aperture arrangement or web arrangement.